Automatic telephone system



July 23,A 1935. H. G. EvERs AUTOMATIC TELEPHONE SYSTEM Filed Jan. 29, 1934 4 Sheets-Sheet l 4 Sheets-Sheet 2 H. G. EVERS AUTOMATIC TELEPHONE SYSTEM Filed Jan. 29, 1934 Lili.

July 23, 1935.

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July 23, 1935.

Filed Jan. 29, 1934 4 Sheets-Sheet 3 www.

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Mw/Gm QM AU'roMA'rIo `TELE?rioNE,v SYSTEM Y Harry G. Evers, Chicagofflll., assignor to Asso'- ciatedvElectric Laboratories, Inc., a corporation of Delaware VAlmiication January 29, 1934, serials@ 708,783

Chicago, Ill., A

20 claims; (ci. `1,19-1'1) Y This invention yrelatesfin-'general to automatic telephonesystems, but more in-particular to small systemssuited for installation in towns or Villages. lAn automatic telephone system of this type Ais generally knowndas a Community Automatic Exchange or C. AX., and mayhave a capacity of about-twenty lines, more orless. Usually the lines are partylines having either bridged orgrounded ringing circuits overwhich such subscribers are signalled by means of code ringing. Provisionis also made fori trunking calls to and from exchanges.

The object ofthe present inventionis distant t. prof videa novel andl improvedrall-relay community automaticA exchange of thefforegoing character.

One of the features yof the invention relates to the all-relay nderA-connector links vfor intercon` necting the various lines in this system.r Anothenfeature of the invention relate manner in which both s to the the trunk lines and subscribers lines are connected to `aiinder-connector link especiallythe line and trunk hunting operations of the finder and connector unitsV relays. I

Another feature of the invention relates'to an improvedAv pulsing arrangement for repeating the pulses received from a calling line. v

Another feature of the invention relates toy circuit arrangements wherebyvthe nderfconnector link switches straight through cutting ofi thelocal talking bridges onrjoutgoingtrunk calls. l

Another featurenoi the invention relate Sft the circuit arrangements for selecting and connect; ing `various code rings'to called subscribers lines. Theseand otherl features of the invention will be apparent from the following detailed description .of the invention.

Referring now to the drawings, comprising Figs.

1 to 4, inclusive, there 1s sho-wn by Ameans,ofthe usual circuit diagrams one of the all-relayrnder'- connector-links, two dim two substation circuits v*by means invention may be describedy and fferent vline ,circuits and of whichthe understood.

Fig. 1 shows'a group or iinder group relays FGR for connecting the line conductors and testconductors of the vvarious groups of lines and'trunk lines to 'one of links.

the iirider-conriectorv all-relay The groups of lines are divided into vfour groups .of rive lines Aeach and are designated yas thev lil, `21),'3ll, and 4B groups. lays lll-4D, inclusive,are for connecting Relayssuch as rethe test and line conductors of their-respective groups to thelink circuit. InV the upper left-hand cornerof Fig.A 1 is shown the line circuit :it l 5 of a line in the lll-group. A plurality of substations such connected-to.vv this line. As .will be seen,

as S are the line Athese conductors terminate connector group relays, such as` relay 2H).r The 1()y circuit is :similar '.to the conductors of this line, or line I5, are multipled and terminate infarmatures `l l `and `Al 2 in the call-v ing or finder end ofthelinks, -while the calling testyconductoraof V this-,line is likewise rnultipled and terminates'rin armaturesilS in the Various 5 links. lThe.y line; conductors fand the Vcalled ftest conductor extend by-wayiof a three-conductor cab1e4 to the outgoing endsof the links wherein in armatures on the last'three line connections in the iiD-group lare connected to trunk lines extending to a distant exchange and terminatem the links similar to the local lines. The trunkgline conductors ,are also connected tov the outgoing end oi` the links inJLai manner. similar .to that described for line I5'. Each grouplofllines hasacommon start conductor, such as'conductors 5 and 5', which extends, as shown; to the r'ider group relays in each link, and also through resistances to' a common start' i'c'onductor 99 which' isV connected in series through all ofthe links. The group of nder units relays FUR. shown to fthe right arefor vconnecting"thel ine vofany'selected group to the control circuits inthe link. LV"-Fig. 2"'shows a group of connector unit relays CUR for connecting the link"to a particular called line in anycalled group as determined by the operated connector group relay. The group of connector group relays CGR are for connect- 0 ing the aoutgoing Aend of ythe'link'to any line in anyxgroup.-f-=' Intheright-handendl oflig. 2 is shown `tl'i'eline circuit of .the grounded line 25 anda pluralityzof substations thereon. This line' d line circuit shown in Fig. 1 and has been altered for use on a grounded line as l"indicated"by the'- circuit changes and 'smallcirclesff Y A Y Line 25 is agroundedline and is connected to theincoming endof the link by the three-conductor'cable extending to armatures 2 I ,22 and 23, inlFig. 1.A V"All of the trunk lines and all of the subscribers lines `infll 'of theA `groups terminate in they outgoing end :of thelink in the manner 45 illustrated by line 25. In addition each linehas an extra ytest conductor,VV such as conductor 234. This extra Atest conductor only connected by a jumper, such as ljumper 249, to the regular test conductor of all trunk lines in argroupbut the desired .ringingde isf @Elfriede Fig. 4 shows another group of relays in the control circuit of the same link.

Briefly the operation of the system is as follows:

When a calling subscriber initiates a call the test conductor of the calling line is marked with calling potential and the calling group is marked in all the finder-group relays all the links. The start conductor is grounded and the finder group relays in the first idle link operate in sequence to find the calling group. When the calling group is found the last operated finder group relay connects all of the conductors of all of the lines in the calling groupto the finder,l

sequence until units relays which now operate in the marked calling line is found. v

When the calling line is found the transfer relay in the. link is operated'to prepare another idle link for use and the calling line is connected to the control circuits of the link in use. The first digit transmitted by the calling subscriber operates impulse repeating relays to 'successively operate` the corresponding connector group relays'. Only the last operated connector group relay is maintained/energized to connect the conductors of the called group to the connector units relays of the link. The second digit reoperates the impulse repeating relays to successively operate the corresponding connector unit relays. Only the last Voperated connector unit relay is maintained energized to connect the conductors of the called line to the link control circuits. The third digit reoperates the impulse repeatingrelays to select the ringing code. If'the called line is idle the ringing interruptor (not shown) transmits ringing current over the selected code ringing conductor to ring the code of the called line.

In outgoing trunk calls the calling line is found in the same. manner as just described and in re sponse to dialling the two digits designating a trunk call the corresponding connector A'group and unit relays operate as before to connect with the nrst trunk in the group. In case the rst trunk in this group is busy then the remaining connector unit relays are successively operated to hunt for an idle trunk in this group. VWhen an idle trunk line is found lthe link switches through cutting oir the local talking bridges. Local call 'Y It will now be assumed that subscribers desires to call subscriber S. Whenithepsubscribcr S removes his receiver a circuit is completed for energizing line relay 8 over the following circuit: from ground by way of armature 18 andresting contact, through the winding of relay 8, over the lower talking conductor I of line I5 through the subscribers substation loop over the upper heavy talking conductor 2, armature TI, and through the upper winding of relay Sto battery.- Relay 8 at armature 86 disconnects the called test conductor 3 from the cut-off relay I at its resting contact and at its working contact grounds conductor 3 which extends by Way of the three conductor cable 4 to busy the calling line. at itsA called terminals, at armature 81 connects the cut-olf relay I to armature I3 by way of armature 66 to mark line I5 as a calling line in the finder group relays. At armature 88 relay 8 grounds start conductor 5 by way of armature 61. and resting contact, thereby marking the calling group in the finder group relays FGR in all the links. Responsive to relay grounding start conductor5 aclrcuit may be traced for energizing the combined start and line relay in the first idle link in the chainas follows: from grounded armature 88, armature 61 and resting contact, conductor 5, resistance RI, conductor 99, armature |03 and resting contact, and through the winding of combined start and line relay |60 to battery.

Relay |60, upon energizing over the abovetraced circuit, at armature |6I and its working contact completes the circuit for energizing slowto-release relay from grounded armature |32. At armature |8| relay |80 prepares a point in the circuit for marginal switch-through relay |30, at armature |82 completes an obvious circuit for energizing slow to release relay I 90, and at armature |83 and working contact connects ground to the lowerv winding'of the transfer line test relay |00. Atarmature I9I relay |90, upon energizing, Aprepares a point in the impulsing circuit, at armature |92 grounds conductor |24 to complete an energizing circuit for relay 360, at armature |93 grounds the connector lock conductor |26 to provide a locking circuit Vfor the connector group and unit relays when the same are operated, at armature |94 and resting contact, disconnects one of the ground connections from the common all link busy conductor ALB, and at its working contact grounds conductor I4 to provide a locking circuit for the finder group'unit relays, the code selecting relays, and other relays inthe link circult."A The circuit for'energizing relay 360 may be traced as follows: from grounded conductor |24 by Way of armature 3|5 and resting Contact, and through the Winding of relay 360 to battery. At armature 36| relay 360 disconnects the rst code selecting relay CI at its resting contact and prepares a circuit for the first connector group relay 2|0 at its working contact, at armature 362 opens thecircuitto-locking conductor |46 at its resting contact and at its Working contact connects'up conductor 2I'I. A1; armature 363 relay 360 at its resting contact opens the even pulse conductor |41 extending tothe code selecting relays, andat its working contact connects up the even pulse conductor extending to the connector group relaysgat armature 364 'and resting contact opens the -circuit extending to the odd pulse conductor |48 extending to the code selecting relays and 'at its Working contact'connects up theodd pulsing conductor to the connector group relays. At armature 365 relay 360 connects dial tone by wayv of vthe dial tone condenser and armature 3I4 to the upper talking conductor |08, at armature 366 preparesa point in its own lock'- ing circuit and at armature 361 prepares a. circuit for energizing relay 350 in series with relay 360,

When ground is connected to the lock conductor I4 a circuit may be traced for energizing the ilrst finder group relay I0 as follows:` from grounded conductor I4, armature I 04 and resting contact, armature |I2 and resting contact, group start conductor 96, varmature 48, armature 38, armature 28, armature I8, and through the winding of slow to operate relay I 0 to battery. Relay I0, upon energizing, closes a locking circuit for itself at armature I 6' before operating the re'- maining armatures. `This locking circuit may beV traced'from grounded lock conductor I4 by Way of armatures 45, 35, 25, and armature I6. Relay I0, upon fullyoperating, closes its armatures I2, I3', etc., to connect all of the lines including lines I2, I3, I4 andv I5 in the I0- group to this link circuit, at armature Il completes thecir'cuit for energizing slow to operate relay 20, at armature I8 opens a point in its original energizing circuit onlyafter the above traced locking circuit has been completed, and at k rto explainl the'` hunting link circuit. vAt armature yto the group testconductor 98.

armature I9 connects thegroup marking ground extending by '-'way-'of conductors 5' and' 56 to conductor 98.` y Y 'f Since relay 29. is a, slow to foperate relay, the group test relay I I9 WilLoperate and open the circuit for'energ'izing relay-20 before the latter can operate in case relay I0 at varmature I9 connects ground to conductor'98.' However, in order operations ofthe finder group' relays FGR itxwill be assumed Afor the time being thatrelay I0 does Ynot connect ground to conductor 98, and therefore relay vI I0 nwill not operate and open'the circuit-to relay 20 before it can fully energize. In this case relay 20 operates its armature 29 after an interval, to first complete its locking circuit by way of armatures 26, 35, and 45to groundedllock conductor I4.l VAt its upper armatures such as armatures 2 I, 22, 23, etc., relay 29 connects all'thelines in1the'29-group to the 25 relay 20 opens the locking circuit 'of relay I9 to causefth'e latter relay to deenergize and open the circuits to the lines in theIll-group. At armature 21 vrelay 20` completes the circuit for slow to operate relay 39, fat armature 28 opens a point in its Voriginal energizing circuit, andY at armature 29 connects the common group start conductor 5' by `way of lconductor 51 In case the start conductor 5 is grounded then the test relay IIU is energized to open the circuit to relay 39 before slofwto'operate relay39 has 'had suicient time to operate its armatures. just described slow to operate relays 39 and 49 operate to connect the linesvof the 39 and' 49 line groups to the linkfand to connect vthe start conductor of such groups tothe group test conductor98.r When the finder group relay corresponding to the calling Vgroup is fully energized, a circuit maybe t'raced for energizing the group test relay I I9 from grounded start conductor, such as conductor 5, conductor 56,-armature I9, group testV conductor 98 ,Y armature I 92,v and' through the upper winding of group test-relay IID to battery. Grou'p'test relay II'9 operates'very quickly to open theA circuitat armature I I2 and resting contact extending to the yfinder group relays so asto open the circuit completed forthe succeeding iindler group relay before thisrelay has had sufiicient time to energize. Atfarma'ture III relay IIB connects ground through resistance IIJ1 to the winding of relay-ISB to maintain relay |69 in energized positionand also for reducing the click in thecalling-subscribers receiverwhen the calling line is connected to ,the-link, at armature-I I3 short circuits its lower winding to make this relay slow to release, and at armature I I2 and working contact connects the grounded lock conductor I4 to the line start c'zondu'ctor `91 by way of resting contact and armature I04. f

f When line ,startcoriductor 91 isgrounded b-y the operation 'of group test relay I 19,'nder unit relay 59 is energized overthe following circuit: from grounded conductor 91 by way of armatures 95, 8.5, 15, and 55, and-through'the winding of slow to operate relay 5il-to`battery. At armature 54 relay A59 completes a locking circuit for itself from grounded lock' conductor I4 by way of the normally closed springs 'controlled 'by armatures 9A, 84, 14, and. vAt armature contact relay 59 opens a point in its original en#- ergizing circuit vonly afterf its locking circuit has been completed andxat its working contact completes the circuit for slow to operate relay 60. YAt its upper armatures relay' connects the line and test 'conductors of lineI I to the line and test cone ing circuit of relay calling line has marked the In the same mannerV asv ltor 5. 55 and resting ductors of the link.l In case relay 20 insteadof relay I0 were operated, then'the upper armatures ofrelay 5I) would connectthe line and test conductors of line 2I to the link. Since line I I Iis not calling, then negative battery through the winding of the cut-off relay is not connected tothe test lead of line II with the result that no circuit is completed for the transfer line test relay II'IIl. Since relay |99 does not operate slow to Vvoperate relayl 60 has had sufficient time to energize and' operate its armatures. The circuit for ener-gizing relay 69-extends by way of grounded conductor 91, armatures 95, 85, 15, and 65, and their resting contacts, and by way of armature 55 and its working contact through the winding of relay 60 to battery. In a manner similarto that described for relay 50, relay 59 completes its locking circuit at armature 64, and also opens thelock- 59 to cause the latter relay to deenergize. At armature 55 and its resting contact relay 69 opens a point in its original energizing circuit-and at its working contact completes the circuit for slow toroperate relay 19. At

its upper armatures relay 69 in asimilar manner connects the line and test conductors of linei tothe link. The nder unit relays 59, 1E), 96 and 99" operate in the same manner as just described until one of the finder unit relays connects the calling line to the link circuit; In .this case the testk conductor with battery potential through the windings ofv cut oil relay such as relay relaycorresponding to the callingline is energized a circuit is completed for the line and tran.,- fer relay Il. Inthis. case since line I5 is the calling line and battery potential through the windings of cuteoff relay 1 is connected to test conductor 9, the finder unit relays 19, .89, and operate in sequence as described, and relay 99 completes the energizing circuit for relay'IeEl as follows: from ground by wayof armature H13y and 1, and whenthe nder unit itsfworking contact, through the lower winding the-upper winding ofr line relay 8 from the negative talkingrconductorl, at armature 18 and resting contact disconnects winding of line relay 3, and at its Working contact completes a circuit for energizing slowto release relay 6. At armature. 66'relay 6 opens a vpoint in the original energizing circuit-of relay 1 and at' armature 61`disconnects groundv from the common start conductor 5 at its resting contact, and at its working contact prepares a locking circuit for itself. Line relay 8 deenergizes when its circuit is opened by the cut-off relay 1, and at armature 86 disconnects direct ground from conduc-tor 3.and substitutes ground on the test'conlductor 9 in place thereof. 'At armature 81 relay 8 opens a point in the original energizing circuit of relay 1 and at armature 88 opens a further point for removing'ground from start conduc- Transfer line test relay YIIl0 energizes very quickly when its circuit is completed by the operated finder units relay, circuit grounding conductor 91 at armature |94 so as toprevent the operation ofthe next succeeding finder unit relay, At armature |94 relay IIII) completesA a locking `:circuit through Yits ground from` the lower and quickly opens the upper Winding from grounded lock 'conductor I4, at armature |02 opens the circuit of group test relay 0 to cause this relay to deenergize. yAt armature |03 and resting contact relay |00 opens the original energizing circuit of line relay |60 and at working contact of armature |03 transfers the start lead 99 to the next finder-connector link by way of conductor 99. At armature |05 relay |00 short circuits its lower winding to connect direct ground to conductor 19 to mark the calling line busy at the calling end by grounding conductor 9 and also to ground conductor 3 by way of armatures `16 and 86 to busy. this line at the called end. At armatures IQI and |06 relay |00 completes a new circuit including the calling subscribers loop for maintainingline relay |60 in operated position. This circuit may be traced as follows: from ground -by way of armature |12 and resting contact, armatures |44 and |36, normally closed springs controlled by armature |22, armature |06, conductor 69, armature 9|, armature II, conductor I throughthe calling substation loop to conductor 2, armatures I2 Vand 92, conductor 89, armaturel I0 I, normally closed springs controlled by armature I2 I, armature ISI and resting contact, armature |4I, through the upper left-hand winding of repeating coil RC, and through the winding of line relay |60 to battery.

Dial tone is now transmitted to the calling line in the following manner. When dialtone is connected to talking conductoil, asgpreviously described, the tone induced in the upper righthand Winding of repeating coil RC is induced intothe upper left-hand Winding of repeatingcoil RC and thence over the previously traced circuit through the calling substation loop in the well known manner.

When subscriber S hears the dial tonesuch subscriber Will dial the rst two digits of the called number in accordance with the line number of the desired subscriber, and then the third digit in accordance with the ringing codev assigned to the'desired subscriber on this line. In response to the operation of the calling device at substation S for the first digit, the circuit extend'- ing over the heavy talking conductor to relay |60 is interrupted in accordance with the digit dialled. Whenever the dialling circuit is interrupted line relay |60 deenergizes and at armature |6| and working contact temporarily opens the circuit to slow to release relay |80, which, however, is maintained energized during the impulsing period due to its slow release characteristics, Aand at its resting contact grounds the impulsing conductor I I8 by way of armature |9| and grounded armature |32. Each time the impulsing conductor ||8 is grounded a circuit is completed for slow to release series relay 3|0 as follows: from grounded impulse conductor I8, armature 302, armature 332 and resting contact, and through the winding of slow to release relay 3|0 to battery. At armature 3|I relay 3|0 completes an obvious circuit for energizing relay 320, andV at armature3|2 opens 4a point in the circuit extending to the extra test conductor 3 I 9. Due to its slow release characteristics relay 3|0 is maintained energized during the impulsing* period, and therefore maintains relay 320 likewise energized.- At armature 32| relay 320 opens a point in the testing circuit, at armature 322 prepares a point in the circuit extending to the two-step marginal busy relay 330, at armature 323 completes a'locking circuit for relay 360 'from grounded lock conductor I4.by.wa`yof armature 355 and resting contact, and .at armature 324 completeszan energizing circuit for slow toV operate relay 3I3 from grounded lock conductor |4 through the normally closed springs controlled by armature 3 I 5.V At armature 3 I4 relay 3|3 opens the dial tone circuit, at armature 3|5 and its resting Contact opens the original energizing circuit forrelay 360, which is now maintained energized overA its locking circuit, and at the Working` contact of larmature 3I5 completes an obvious locking circuit for itself from grounded conductor |24, as well as opening its original energizing circuit at the normally ,closed springs controlled by .armature 3|5. y

The firstr time impulse Vconductor I I 8 is groundedgdiferential relay 380 is energized'over the followingcircuit: from ground on the impulse conductor IIB, armature 302, armaturev 332 and resting contact, armature 393 and resting contact, and through ythe lower winding of relay 380 to battery. At` armature 38| relay 380 connects conductor 3.13 to conductor2|1 for energizing the rst connector group relay 2|0, as follows: from groundedlock conductor |26, armatures 241, 231 and 221, conductor 2|1, working contact and armature 362,v resting contact and armature 352, armature 38|,v armature 35| and resting contact, armature 36 I and working contact, conductor 313, and through the winding of relay 2I0 to battery. Atarmature 382, relay 380 grounds the odd pulse conductor 311v without effect at this time because armature 2291s not operated, at armature 383 prepares-a circuit for the upper winding of differential relay 380, at armature 384 and its working contact completes a circuit for maintaining differential relay 380 energized and for shortcircuitingthe lower winding of relay 390 as follows: from ground on the impulse conductor I I8, armature 302, armature 332 and resting contact, armature 393 .and resting contact, through the lower Winding of relay 390, working contact and armature 384, armature 324 to grounded lock conductor I4. At the end of the rst impulse when line vrelay |60 again energizes, ground is removed from impulse conductor II8 with the result that the short circuit around `the lower winding of .relay 390 is removed and relay 390 now energizes in, seriesA with the lower winding of differential relay 380 from grounded lock conductor I4, armature 324 and armature 384 and working contact, through the -lower winding of relay 390 and the lower winding of differential relay 380 to battery. At armature 39| relay 390Vprepares the circuit Vfor grounding the even pulse lead 315, at armature392 prepares a point in the ringing circuit, `at armature 393 and resting contact opensa point in the original energizing circuit through the lowerwinding of differential relay 380 and at its working contact prepares a circuit for the upper winding of relay 390, and at armature 395 completes a circuitV for energizing relay 310 as follows: from grounded lock conductor I4, armature 324, armature `395 and through the Winding of relay 31|)v to battery. At armature 31| relay 310 closes a shunt around armature 39|, and at armature 312 prepares a locking circuit for itself by Way of resting contact of armature 384 independent of armature 385. In response to the'second impulse conductor IIS is again grounded, and at this time a circuit may be traced for maintaining relay 390 energized through its upper winding and for deenergizing the differential relay 380 as follows: from ground over the impulsing circuit as previously described to armature 393, and from thence by Way of its.working contact, resting contact second connector-group relay line and-test conductors of the tact, through the windingl of` relay 23@ tobattery; Atitsupper armatures lrelay 233 connects the line and; armature 303 throughY the upper 'winding of relay. 398. to battery. onmain'taining Yrelay 39|)A energized, and by way of armature 383 through the upper winding .off differential relayv 380 Yto batteryY to'cause the diife'rentialrelay.,tofdeen-v ergize. relayv38 are energized at .this timeand'since these windings areequal and oppose eachother,

i ing circuit for connector group relay relay 380 therefore deenergizes.

v 'Whenconnector group 2m. energized over :the previously traced circuit, said relay` atits upper` armatures :connected all of `the, lines in the Iogroup to the'link,.at armature "2|8 completes .an lockingv circuit vfor itself through` armatures 221, 231, 241Jand'grfounde'd connector `lock conductor, |26, and, at armature;2|9 `prepares the circuit for.l relay 220'. f Differential relay 38S, upon deenergizing, at armature 38| opens the original energizing'cira cuitoffrelay 2K3, which vis now maintained energized over its locking circuitat armatures 383 and 384 simultaneously opens thecircuits through itszupperand lower` windings, respectively, while at theresting contact of: relay YV383 completes the previouslyv traced locking circuit for relay 310. At yarmature 382 relay 38|) disconnects ground from the odd pulse conductor 311 at its working contact and at its resting contact connects ground to the even pulseA conductor 315 for energizing the 22ias follows: from ground .by wayof armature 364;,and resting contact, armature,382 and resting Contact, through armatures 39| and 31|.'in multiple, armature' 3.53 andfresting contact-armature 363 and workingI contact, conductor 315, armature 2|9 andV `through the winding of relay 220 to battery.

At its .upper armatures relay 22||vconnects the vrZIJ-groupv to the link; at armature 221 opens the locking circuitV `of relay 2|8 which deenergizea Yat-armature ,228, completes its ownlockingcircuit from grounded lock conductor |26 and at armature 229'connectsr the odd pulse conductor 311 to the winding` of relay23ll.v

When line `relay |53 energizes at the end of the second impulse ground is removed from conductor` H8, thereby opening th'evcircuit extending to the upper winding of relay 398, whereupon the latterl relay deenergizes. The impulse .repeating relaysY y, 333 Vand :393 are now the same asat the start-of.

the impulsing period and in'gcasemore than two impulses are transmitted foritherst'digit'relay- 383 is again energized at the start of the third impulse in the lsame Amanner as previouslyde- 1 scrihed'for the first-impulse. A13-armature 384 and resting contact the locking circuit-to'relay 310 is;y

openedwith the `result thatthe latter relay nowV deenergizes and in response tothe operation of armature 382 ground is connectedl tothe odd; pulse conductor 311 for energizing connector group relay 2331as follows: from groundk by wayA of; armature I-land restingcontact, armature 382 and its working contact, armature 354 and restingfcontact, armature 36d and'working conodd pulse conductor 311, armature'229 and and testconducto-rs of all the lines in the 33- grcup to the link, at armature231 opens the locking circuit o relay223 which thereupon deenergizes, at armature conductor`31-5-to relay 248.

Since both thezwindings oil-differential*I 233 completes its'own lockingcircuit from grounded connector lock conductorV |26, and at armature 239fonnects the even pulse the `third impulsefrelays'SS 'and 319 reenergizek in the `'same 'manner ias' previously described. When linerelay |80 deenergizes at the start of the fourth impulse' the circuit through the upper winding .of differential relay 335i is again completed with thefresult that `the diierentialrelay 383 now deenergizes Yto vtransmit an impulse over .the even pulseconductor 31.5.to complete an energiz- 248.' This circuit 'may betraced from ground at the 'resting springs vof armature 334, armature 332 and resting contact, andirorn'thencev over the previously traced circuit tothefeve'n pulse conductor 315,` through armature and the winding` of relay 23u toy battery; t-*armature 241'relay 243 opens the locking circuit of connector, group relay 230 which causes this relay to deenergize. At its upper armatures relay243 connects the line and trunk conductors in the-,sS-'group to the link, at

armature 26H5 prepares: apoint Yin the trunk'.

switch-through circuit; andl at armature 243 com# pletes a locking 'circuit for itselfirom grounded'. lock'conductor. |23. Connector grouprelay1230l upon 'deenergizing disconnects Lthe lines of the.

3J-group from the link. .*Atlthe `end'of thefourthv impulse, when line relay yHflreenergizea the cir-` cuit'through the upper winding of .relay 390 is opened in the same' manner as previously de-` scribed withcthe result that thisv relayV now deenergizes. n.

'In ,this.case,"v since subscriber Sis calling subscriber S,only,two impulses have yloeen transmit'-Vv ted withthe'resultlthat connector;Y group relay 22|! isenergizedY 'as previously described to connect the lines.V in the `gr,oup to thelink;` After the rst'seriesof impulses slow to` release relay 3H)` energizing `relay 350. inV series with relay 330, as

follows: From grounded lock conductor |4,'nor.

mally closed rsprings controlle'dby armature 323,

k armature 331,;throu'gh the upper Winding of relay 35.3` and'through the winding of relay 330'to battery., :Relay 36|) is maintained energized over thiscircuitwhile relay v35|) atarmature 355 pre-V pares a locking. circuit for itself. At armatures 35|'.to, 35,4,cin`clusive, relay 353 'connects up the control*conductors` extending to the connector unit'relays. 1:.1 91; i Subscriber Snow dials .the 4unit digit or digit 5 ofzthe .calledlineL In response thereto line relay ltl'again .deenergizesrfive'timea In. response to the first, impulse slow to release relayv 3|!) again energizesioverxthe circuit previously traced,l and the impulse repeating' relayV 383 likewise again energi'zes. .Atzarmature 3|| relay3l0againcompletesfthe -circuit forenergi'zing relay 323 and theA latter relayat armature 323 completes. a locking* circuit fromv grounded lock'conductor I4 through' the lower AWinding of relay-350v to hold this relay inv energized position while,l at the normally closed springs controlled :by armature 323 the circuitv through' the upper Winding of relay v353 and thev winding of 363 is opened to cause the latter relay to deenergize. yAtarmature 324 relay` 32B again connectsgrounded lock conductorvv I 4 to Varmature 384;'At Varmatures 35| tox334, inclusive, relay.

33D .f disconnects the controlY conductors from. the relays and prepares a circuitfori connecting the .control conductors tov the/code selecting relays'CRS in `li.g..v3,ra'-nd at armature lconnector group completes va circuit for 365 disconnects dial tone. At armature 38| relay 380 completes a circuit for energizing the rst connector unit relay 250 as follows: from grounded connector lock conductor |26 by way of armatures 296, 286, and 266, conductor 256, working contact and armature 352, armature 38|, armature 35| and working Contact, conductor 314, and'through the winding of relay 250 to battery.

At armature 251 relay 250 completes a locking circuit for itself fromV the grounded connector lock conductor |26, and at armatures 258 and 259 prepares a circuit for the second connector unit relay 269. AAt its upper armatures relay 250 connects the line and test conductors of line 2| to the link. When line relay 60energizes at the end of the rst impulse, relays 390 and 310 energize from ground on vthe lockconductor I4 in the same manner as previously described. When line relay |60 deenergizes in response to the second pulse, differential relay 380 deenergizes while relay'390 is maintained as previously described. AtV armature 382jrelay 380 completes a circuit for energizing the second connector unit relay 260 as follows: from ground by vway of armature 304 and resting contact, armature 382 and resting contact, armatures 31| .andk 39| in multiple, armature 353 and working contact, conductor 316, armature 259, and/through the winding of 30 relay 260 to battery. At armature 261 relay 260 completes a locking circuit for'itself from the grounded connector lock conductor |26, at armature 266`opens the locking .circuit of relay 250 to cause its deenergization and at armatures 268 and 269 prepares the circuit for the next connector unit relay 210. At its upper armatures relay 260 connects the line and test conductors of line 22 to the link. Relay 250, upon deenergizing, at its upper armature disconnects the line and test conductors of line 2| from the link. At the end of the second impulse when line relay I 60 reenergizes the circuit through the upper Winding of relay 390 is opened with the result, that this relay now deenergizes.

When line relay |60 deenergizes in response to the third impulse, differential relay 380 is again energized as previously described. .At armature 382 relay 389 completes a circuit 'for energizing relay 210 as follows: from ground by way of Y armature 304 and resting contact, armature 382 and workingcontact, armature 354 and working contact, over the odd Y pulse Aconductor 318,

through armature 269 and the winding of relay.

210 to battery. At armature 211 .relay 218 completes a locking circuit i for itselfgfrom the grounded connector lock conductorzlZG, atarmature 216 opens the locking :ircuit'oi-relay1260 which thereupon deenergizes, at Iarmatures 218 and 219 prepares the circuits for energizingrelay 280, and at armature 215 prepares a point in-` the 'switch-through circuit. Atits'upper .armaturesv relay 216 connects the line and test conductors of line 23 to the link. Relay 260, upon deenergizing at its upper armaturesdisconnectsline and. test conductors of line 22 from the link. At the end of the third impulse when line relay |60 reener.

gizes, relays 390 and 310 are again energized over the circuit previously traced.

When line relay 60 4deenergizes in response to the `fourth impulse the circuit through the upper windings of i relays 380 and pleted to cause the deenergization of differential relay 380 and to maintain relay 390, in operated position. At armature 382 relay 380, upon deenergizng, completes .the circuit for energizing re- 390 is again com-` lay 280 as follows: .from ground by way of arma; ture 304v and resting contact, armature 382 and resting contact, armatures 31| and 39| in multiple, armature 353 and working contact, over the even pulse conductor 316 through armature 219 and the winding of relay 280 to battery. At armature 281 relay 280 completes a locking circuit for itselfirom grounded lock conductor 26, at armature 286 opens the locking circuit of relay.210 which thereupon deenergizes, at armatures 288 and 289 prepares the circuits for energizing relay 290 andV at armature 285 prepares another point in the switch-through circuit. At its upper armatures `relay* 280 connects the line and test conductors of line 24 to the link. Relay 210, upon deenergizing, at its upper armatures disconnects the line and test conductors of line 23 from the link. When line relay |60 reenergizes at the end of the fourth impulse the circuit through the upper winding of relay 398 is opened, thereby causing the deenergization of this relay.

When relay |60 deenergizes in response to the fifth impulse, relay 380 again energizes to complete a circuit forenergizing relay 290 as follows: from grounded armature 304 over the previously traced circuit to the odd pulse conductor 318 and thence by way of armature 239 and the winding of relay 290 to battery. At armature 384.relay 380 causes the deenergization of relay 310 as previously described. At armature 291 relay 290` completes a locking circuit for itself from grounded lock conductor |26, at armature 296 opens the locking circuit of relay 280 to cause its deenergization, and at armature 295 preparesanother point in the switch-through circuit. At its upper armatures 29|, 292, 293, and 294 relay 290 connects the line and test conductors of line 25 to the link. Relay 280, upon .deenergizing at its upperrarrnaturesv disconnects the line and test conductors of 'line 24 from the link. When line relay |60 reenergizes at the end of the fifth impulse relays 390 4and 310 again energize as previously described. v

After the impulsing period slow to release relay 3|0 and then relay 320 deenergize. At armature 324 relay 320 opens the circuit .of relays 380 and 390 to cause the deenergization of these relays, and at armature 323 opens the locking circuit extending to the lower winding of relay 350 to cause the latter relay to deenergize. At armatures 35| to 354, inclusive, relay 350 prepares the circuits` extending to the code selecting relays CSR. i kSubscriber S now dials the last or ringing digit assigned to the desired subscriber on line 25. Inv response to the first impulse linerelay |60 again deenergizes and again closes the circuit for energizing slow to release relay 3 I0 and differential relay 380. At armature 3| I relay 3|0 again completes the circuit for energizing relay 320. At armature 32| relay 320 opens a point in the test circuit and at armature 322 connects the busy two-step marginal relay 330 to test conductorV |25. Relay 330, upon energizing, at armature 38| completes a circuit for energizing the first code selecting relay CI as follows: from grounded lock conductor I 4 by way of armatures |54, |59, |61, `|11 and |18, conductor |46, resting contact of armature 362 and said armature, resting contact and armature 352, armature 38|, armature 35| and resting contact, armature 36| and resting contact, conductor and through the windf ing of relay CI to battery. At armature |96 relay C| prepares a point for connecting the ,code ringing conductor 2-| to conductor |39, at arductor i4, at armature mature |91 prepares a circuit for connecting the code ringing conductor to the called line, at armature |98 opens a point in the locking circuit of relay C5, at armature |99 completesa locking circuit for itself from grounded lock conductor lll, at armature |49 prepares a point in the circuit for relay C2, and at armature |53 connects ther test conductor of the called line to the windingl oi two step marginal busy relay 338' for testing purposes. Y

Before describing the testing arrangement it is believed advisable to explain the operation of the code selecting relays in response tothe code selecting digits dialled thereto. peating relays 389, 396 and 310 operateV in thel same manner as previously described to transmit ground impulses from armature 394 to the even and odd conductors |41' and |48 to the 'code selecting relays. When relay 389 deenergizes in respense to the second impulse of the code ringing digit a circuit is completed over the keven pulse conductor |41 for energizing relay C2 as follows: from groundv by way of armature 394-and resting Contact, armature 382! and resting contact, ar'-v matures 39| and Sii in multiple, armature 353 and resting contact, armature 383 and resting contact, even pulse conductor |41, armature |49 and through the winding of relay C2 to battery. At armature |85 relay C?. prepareslthe code ringing conductor 2-3, at armature |86 connects up the `code ring conductor 2-'-2, at armature iS'i opens the locking circuit of relay C| which thereupon deenergizes, at armature |88 completes a locking circuit for itself from grounded lock con- |89 prepares a circuit for relay C3, and at armature |95 completes another point in the test circuit. Relay'CI, upon deenergizing, at armature |98 prepares a locking circuit or relay C5, at armatures y|96 and |91 disconnects the code-ring conductors 2| and at armature |49 opens the original energizing circuit of relay C2, and at armature |53 opens a point in the test circuit, which circuit, however, is maintained closed at armature |95.

In response to the third impulse, relay upon energizing, completes the circuit for energizing the third code 'selecting relay C3 over the `odd pulse conductor |48 as follows: from` ground by way of armature-384 and resting con tact, armatureV 382 and Working contact, armature 354 and resting contact, armature 364 and resting contact, odd pulse conductor |48, armature |89 and through battery. At armatures and |16 relay C3 prepares the circuit for the code ring conductors 3| and 3--3, at armature |11 opens the l0ck` ing circuit of relay C2 which thereupon deenergizes, at armature |18 completes a locking cir-V cuit for itself from grounded lock conductor I4,

at armature |19 prepares a circuit for relay 04,1

and at armature |84 maintains the test circuit closed.A Relay C2, upon deenergizing, at armatures |85 and |86 disconnects the code ring conductors v2--3 and 2 2, and at armature |89 opens the original energizing circuit or" relay C3.

Relay 330 deenergizes in response' to the fourth impulse and again grounds the even pulse conductor |41 tocomplete a circuit by way of armature |19 for relay C4. At armatures |65 and |66 relay C4 connects the code ring conductor 3--2 and |-e2,'at armature |614 opens the locking circuit of relay AC3 which thereupon deenergizes, |68 completes a locking circuit forv at armature itself from grounded lock conductor i4, at'arrnature |69 .prepares a circuitv for Vrelay C5,xand at The impulse resco,

the winding of relay C3.toV

lock conductor armature|14v maintains the'test circuit closed.

Relay C3 deenergizes and` opens the circuitto the selected code ring conductors. In response to the fth impulse relay 388 again energizes to ground the odd pulse conductor |48 to complete an energizing circuit for relay 'C5 by way of armature |69. At armatures |51 and |68frelay C5 connects the code ring conductors |-4 andy |,-'3, at armature |59 opens the locking circuit of relayC4 whichV thereupon deenergizes, at arma' ture v|t2 `cornpletes a locking circuit for itself from grounded lock conductorflibyway'o arma-y ture |98, at armature |63 prepares the lcircuit for relay C6, and at armature |64 maintains the test circuit closed. Relay C4 deenergizes and disconnects the selected code ringing conductors and at armature |68 opensy the original energiz-V ing circuit of relay C5. 1 i

Relay 388 deenergizes in responseto the 'sixth' impulse to ground the even pulse conductor |41 vthereby completing an energizing circuit for-refvv upper groups of'code ringing conductors toicon-I ductor |39. At armature |55 relayC6 completes a locking Vcircuit for itself from grounded conductor i4 and at armature |56 maintains the test circuit closed.

When relay 380 energizes in response to the seventh impulse said relay completes a circuit-for energizing relay CI over the following circuit: from grounded lock conductor '|4, armature |54 andworking contact, armatures'll, |11 and |81; conductor |46, resting contact and armature 362, resting contact and armature'352, armature 38|, armature 35| iand'resting contact, armature v36| andA resting contact, conductor |45, Vand throughthe Winding of'relay C| to battery. .Re-2 lay CI again energizes and in this instance at armature |96 prepares a circuit'for connectingup the code ring conductor 2-|.` At armature |99 relay C| .completes a locking circuitV for itsellatv armature |49 prepares'a circuit for relaylCZ and at armature |98 opens the lockingv circuit of re-y lay C5A which thereupon deenergizes.

Relay 388deenergizes responsive to the eighth impulse'to ground thel even pulse conductor |41,v to cause the reenergization oi relay C2.` At armai-i, ture' |85 relay C2 connects up the second code ring conductor 2-'3, at armature |81 opensthe lockingV circuit of relay'CI, at armature |88com pletes a lockingcircuit Vfor itseltfromigrounded |4, and at'armature |89 prepares the circuit for relay C3. In the same manner as just described relay C3'is energized in responseto the ninthimpulse, and relay C4 is energized in response to the tenth impulse, thereby selecting thedesired code ring conductor in accordance with the digit dialled. It will be noticedv that the; lenergized in response'v code selecting relay C6 is to the sixth impulse, and is thereafter maintained in energized position for the remaining impulses in case more than sixv impulses are transmitted'. It will, also be' noted. that the energization of .a

code selecting relay lcauses the deenergization of the previously operated code selecting relay', so that the proper accordance with the digit dialled.

When'` the test circuit was closed in response to the operation of relay C the following ycircuit is closed tolthev two-step busyV relay; from armaturecode ring conductor is selected'in 2||3 of the called line circuit, the multiple connections of the test conductor of called line, armaturev 223, armature 293, test conductor armature |33 and resting contact, conductor H9, through the upper Winding of test relay 390, conductor |38, armature 53, conductor |25, through resistance 325, armature 322, and the Winding of two-step marginal busy relay 33B to battery. In case the called line is busy ground will be connected to armature 203 with the result that the busy relay is energized in its first step over the previously traced circuit. Two-step relay 330 operates only its armature 334 to prepare the circuit for fully energizing itself when relay 329 later yon deenergizes. Test relay 390 will not energize in the abovetraced circuit due to the resistance in the winding of. busy relay 330 and resistance 325. After the last impulse of the ringing digit slow to release relay 3 E deenergizesand opens the circuit to relay 320 which relay thereupon deenergizes.. At armature 324 relay 323 opens the circuit of relays 389 and 390, and at armature 322 completes the circuit for operating the busy relay through its second step in case the same is at the I timeenergized in its .rst step, as follows: from ground at armature |92, conductor |24, armature 334 and workingcontact,r through the normally' closed springs controlled by armature 352, through the normally closedsprings controlled f by armature 322, and' through the winding of the release of the apparatus in two-step relay 332|.to battery. Relay 33D, thereupon energizes in its second step and operates its remaining armatures indicated by the Roman numeral II. At armature 33| relay 33B connects busy tone through the right-hand winding of the repeating coil RC to relay and battery. vAt armature 332 and resting contact opens a point in `the impulsing circuit, at armature 333 grounds conductor |23 for a purpose to be more fully described in making revertive calls, at armature 335 prepares a circuit for .the trunk hunting relay 34B, and at armature 336 prepares another circuit used in making reverting calls. At this time the.

busy tone is transmitted from the busy tone source through the busy tone condenser, armatures 34| through the upper right` and 33|, conductor |08, hand Winding of repeatingcoil RC and through the windingof relay |18 to battery. Busy tone is thereby induced into the left-hand windings of the repeating coil RC in the well known manner to transmit the tone to the calling subscriber over the heavy talking conductors.

When the calling subscriber hears the busy tone such subscriber will replace his receiver to cause a manner to be more fully` described hereinafter.

Assuming now that theline called is idle instead'of busy, then no circuit is completed for busy relay 335i, and therefore the busy relay does not energize in its rst step. After the code ringingY digit, relays 3|0 and 320 deenergize aspreviously described. Relay329 causes the deenergization of relays 380 and 390, if energized, and at armature 32| completes the circuit for energizing the connectortest relay 300 in series vwith the cut-off relay of armature |92, conductor |24, armature 334 and resting contact, armature through the operated armature on the code selecting relay, such as armatures |53 or |95, conductor |38, through the upper winding of relay 300, conductor H9, resting contact and armature |33,.conductor armature 293, armature 223,

armature 203 and resting contact, and through'` 20| as follows: from ground by way:

32|, conductor |25,v

armature 236 relay 20| connects ground extending from the link circuit to conductor 233 to mark this line as busy in the calling end of the link, at armature 291 opens the circuit extending to line relay 200, and at armature 293 completes the circuit for energizing slow to release relay 292.

Relay 330, upon energizing, rst closes its ar mature 335 to complete a locking circuit through its lower winding, aswell asv an energizing circuit for completely operating this relay from grounded lock conductor i4. `At armatures 335 and 335, relay 336 connects the talking conductors of the called line to complete the talking circuit, at armature 332 opens a point in the impulsing circuit, at armature 393 connects the pick-up lead extending to the code ringing interrupter to the upper winding of relay 399, and at armature 334 short circuits the upper windiitcr of test relay 330 and likewise connects direct ground to test conductor to maintain this line busy in both the calling and the called ends of the link.

The pick-up and hold conductors shown directly above relay 344 extend to a code ringing interrupter (notshown) wherein the pick-up conductor is grounded at the start of a ringing code cycle while the hold conductor is grounded near the start of the ringing cycle and is maintained grounded until the end of the ringing code cycle is reached. When the pick-up conductor is grounded a circuit may be traced for energizing relaygl as follows: from ground via pick-up conductor, armature 345, normally closed springs controlled by armature 394, working contact and armature and through the upper winding of relay 39?: to battery. At armature 394 relay 399 completes a holding circuit vfor holding itself maintained in operated position during the entire ringing cycle from ground by way of hold conductor, armature 394 and working contact, working contact and armature 333,V and through the upper Winding of relay 383 to battery. At armature 392 relay 390 connects the selected code ring conductor to the called line.

Assuming now that the code ring digit of the called subscriber is Sthen the fth code selector relay or relay C5 is energized to connect the code ring conductor |-3 tothe called line. Ringing current from the code ringing interrupter. is connected to this conductor to produce one short ring followed by a pause and then three vshort rings. 'I'heringing circuit extends from the generator at the ringing interrupter over code conductor |-3, armature |58, resting Contact and armature |52, conductor |39, working contact and armature 392 armature .39| conductor |4, armature 252, armature 222, conductor v232, and from thence tothe ringers and ground at the substations on this line. Ring back tone is transmitted tothe calling subscriber in the following manner: from generator to armature 33|, the ring-back tone condenser, conductor |08, through the upper right-hand winding of repeating coil RC to relay |79 and battery, from `whence the ring back tone is induced into the left-hand Winding of the repeating coil RC in the. well known manner to transmit the ring Yback tone to the calling subscriber.

At the end of the ringing cycle ground is disconnected from the hold conductor in the ringing interrupter with the result that relay 390 now deenergizes to prepare a circuit at armature 392 for the back bridge .relay |711. In case the called subscriber has not answered in response to his ringing code .the pick-up conductor is again grounded after an interval to again cause the again deenergizes when.

energization of relay 390. The ringing code is again transmitted to the called line and relay 390 ground is removed from the hold conductor in the ringing interruptor. If the subscriber has answered in the meantime the deenergization of relay 390 now completes a circuit for energizing back bridge relay |10 as follows: from ground at the substation through the left-hand winding of the induction coil, through the receiver and impulse springs, conductor 232 and from thence over the previously traced ringing circuit to armature 30 l, armature 392 and resting Contact, conductor |08, upper right hand winding of repeating'coil RC, and through the winding of relay lli) to battery.

In case the subscribers on this line should have their ringers bridged across the two talking conductors then the generator return circuit would be traced through the substation loop to conductor-23 I and thence by way of armatures 22| and 29|, conductor IiE, armature 305, to ground at armature 341.

Relay i10, upon energizing over the above traced circuit, at armature I'li opens a point in the circuit used in making reverting calls, at armature |12 and resting contact removes the short circuit from around relay |30 to permit this relay to energize in case the calling line is in non-grounded line, and at the working contact of armature |12 prepares a point in the circuit for energizing the battery reversing relay |20. At armature |12 and working contact relay |10 grounds conductor |29 to| complete an energizing circuit for the ring cut-oil relay 31% by way of the normally closed springs controlled byarmature 3&3. At armature 305 relay Slifi opens a circuit to the upper winding of relay 300 to prevent the reenergization of the latter relay when the pick-up conductor is again grounded, at armature 340 completes a locking circuit for itself from grounded lock conductor I4 as well as opening its original energizing circuit, and at armature 341 disconnects ground from the lower talking conductor.

In. case the calling line is a grounded line similar to line #25, then relay |50 does not energize because it is short circuited from ground on the positive line conductor. This ground will extend over the positive line conductor I, armatures I I and 9|, conductor E9, armature |00, normally closed springs controlled by armature i22, armature |33 and resting contact, armature |40, through the lower left-hand winding of repeating coil RC, and'through the winding of relay |50 to ground. Since relay E50 does not energize, battery revt ng relay |20 likewise is not energized to reverse battery to the calling line.

In case the calling subscriber is on a metallic line like line I5, then relay I 50 energizes over the calling subscribers loop in series with relay |60. At armature I5! relay |50 completes a circuit for energizing the battery reversing relay |20 from ground at the working contact of armature i12. At armatures I2I and |22 relay |20 reverses battery to the calling line for supervisory purposes such as operating a meter or for controlling a payf-station. In this case the talking circuit extends from the .ground through relay |50 through the lower left-hand winding of repeating coil RC, armature |44, resting contact and 'armature |36, armature |2| and working Contact, armature IOI, conductor 09, armatures 92 and I2, and conductor 2 through the calling substation loop to conductor I, armatures and SI, conductor 69, armatures |06 and |22, armature f |31 and resting contact, armature |4|, through the upper left-hand winding of repeating coil RC, and through the winding of line relay |60 to battery. Talking battery to the calling vline is furnished through the windings of relays |50 and |00. In case the calling line is a grounded line, such as line 25, the line conductors in the link extending to this line are not reversed and the local battery at the substation circuit provides the talkin-g battery. The talking circuit to the called line extends by way of conductors 23| and 232, armatures 22| and 222, armatures 29| and 292, conductors ||4 and ||5, armatures 30| and 300, conductors |08 and |09, through the upper and lower right-hand windings of repeating coil RC to battery and ground through the windings of relay |10 and |13. Talking battery on grounded line, such as line 25,"is furnished at the substation,v while talking battery through the windings of relays |10 and |13 is furnished to metallic lines, such as line I5.

After conversation and responsive to the called subscriber replacing his receiver, the circuit to back-bridge relay |10 is opened whereuponthis relay deenergizes. At armature |12 and its working contact relay E10 opens the circuit of battery reversing relay |20 to cause its deenergization and at the resting contact of this armature short circuits the winding of relay |50 to cause it to deenergize. Battery reversing relay |20, upon deenergizing, reverses battery connections to normal for supervisory purposes. Line relay 'deenergizes in response to the callingsubscriber replacing his receiver and at armature |251 opens the circuit to slow to release relay |80. After an interval slow to release relayv .|80 deenergizes. At armature I82'r-elay |80 opens the circuit of slow to release relay |90 and at armature |83 disconnects ground from test conductor 10 to remove the busy ground from the calling line and to open the circuit to the cut-oirl relay 1 to cause the deenergization of the latter relay. Cut-off relay 1, upon deenergizing, opens the circuit to relay 6 at armature 18, at armatures 11 and 1S reconnects the line relay B to ground and the line conductors of line I and at armature 16 disconnects the Vcalling test conductor 9 from the called test conductor 3. Relay 6 deenergizes after an interval and restores the line circuit to its normal condition.

After an interval slow to release relay |90 deenergizes and at armature |92 disconnects ground from conductor |24 to open the locking circuit of relay 3|3'to cause its-deenergization and to open the locking circuit to busy relay 330 in case the same is energized. At armature |93 relay |90 disconnects ground from the connector lock conductor |20 tov cause the deenergization of the operated connector unit relay and the operated connector group relay. At armature |94 relay |90 disconnects ground from the lock conductor i@ to cause the deenergization of relay |00, the deenergization of the operated code selecting relay, the deenergization of the operated i'lnder unit relay and the operatednder group relay, and the/deenergization of relays 300 and 344i Relay BIS, upon deenergizing at armature 3|4 prepares'the dial tono circuit, at armature 3|5 prepares the circuitv for relay 360 and at armature SIG prepares the permanent disconnect circuit. The operated connector unit relay 290 and the operated connector group relay 220 release and disconnect the called line from the link as wellv asopeni'n'g the circuit to cut-off relay 20|. The deenergization of relay 20| opens Athe circuit of slow to. release relay 202 which deenergizes after an interval. At amature 201 relay 20| again connects the line relay 200 to line conductor 232.

Relay |08, upon deenergizlng, at armatures IDI and |06V disconnects the talking conductors, and at armature |03 prepares the start circuit for relay |68. The operated code selecting relay C5 deenergizes when ground removed from lock .conductor I4 to restore the code selecting relays to normal. In case the digit 5 or a larger digit has been dialed for the ringing digit, then code selecting relay C6 is likewise deenergized when ground is removed from lock conductor I4. The operated nder unit relay 90 and the operated -nder group relay I0 deenergizes and disconneet the line and test conductors of the calling 'line from the Relay 390, upon deenergizing, at armature 3.04. disconnects ground from the test conductor of the called line and relay 344 deenergizes to restore the link circuits to normal. All of the apparatus and relays are now in their normal position and may be used on subsequent calls.

Reverting calls A `description will now be given of the operations whichV take place when a subscriber calls another subscriber on his own line. Assuming now that subscriber S desires to make a reverting call and ca ll' another subscriber on his own line, and that in response to the removal of the receiver at substation S the rst .idle link is auto.- matically connected to line circuit #I5 in the same `manner as previously described. When subscriber S hears thev dial tone such subscriber Will dial vthe directory number of the desired called subscriber. In this case, since the desired subscriber is on the same line with subscriber S, the rst two; digits will be I and 5, While the third digit or code ringing digit Will be a different digit than subscriber S. In response to the first two digits I and 5, the relays in the link circuit operate i-n the same manner as previously described to connect the calling line to its` own line circuit.

In response to the code ringing digit the proper code selecting relay is operated to select the code ringing conductor corresponding to the desired subscriber, and the operation of the rst code selecting relay completes a circuit for energizing the two-step busy relay in its rst step as follows: from ground by way of Working Contact and armature |83, armature |05, conductor 19, armatures 93 and. I3, conductor 9, amature 16, resting contact andY armature 86, conductor 3 included in the three-conductor cable 4, armatures 2 Ig3 and 293, conductor ||1, armature |33 and resting contact, conductor H9, through the upper winding of marginal test relay 300, conductor |38, through the operatedv lower armatures of the code selecting relays, such as armature |53, conductor |25, resistance 325, armature 322, and through the Winding of two-step marginal busy relay 330 to, battery. Marginal relay 300. does not energize over this circuit while the two-step marginal busy relay 330 operates only its armature 334 in its first step. When relays 3|0 and 320 deenergize after the impulsing period, relay 320 at armature '322 completes the previously traced circuit from grounded conductor |24 for energizing the two-step busy relay 330 in its second step. At armature 33| busy relay 330, upon energizing, in its second step, connectsY the busy tone to the calling line in the same manner as previously described. At arma- :ture 333 lrelay 330' grounds conductor |23 to prepare a circuit for maintaining slow to release `relay |90 in operated position and at armature 3,36 prepares a point in the circuit for the reverting call relay |40.

When subscriber Shears the busy tone such subscriber will replace his receiver, thereby opening the circuit through the line relay |50 which thereupon deenergizes. However, since the called subscriber is on the same line as the calling subscriber the operation is somewhat different, and will be described in detail. Line relay |60, upon deenergizing, at armature |6| and its working contact opens the circuit to slow to release relay |80, and at its resting contact completes a circuit for maintaining `the cut-01T relay 1 in line circuit |5 in energized position as follows: from ground by way of armature |32, armature |6| and resting contact, armature |9I, conductor I I8,

armature 302, armature 332 and working contact, f

conductor I9, resting Contact and armature |33, conductor ||1, armatures 293 and 2 |3, conductor 3` included in cable 4, armature 86 and resting contact, and through the winding of relay 1 to battery. After an interval slow to release relay |80 deenergizes. At armature |82 relay |80 opens the circuit of slow to release relay |90, at armature |83 and working contact disconnects ground from conductor 19, and at its resting contact cornpletes the circuit for energizing reverting call relay |40 as follows: from the ground maintaining the cut-off relay 1 energized over conductor 3 as previously described, and thence by way of armature 86 and resting contact, armature 13,

conductor 9, armatures I3 and 93, conductor 19,

armature |05, armature |83 and resting contact, conductor |28, armature 335, conductor |21, and through the winding of reverting call relay |48 to battery. At armatures |4| and |44 relay I 48 opens the circuit extending to the calling line and at armature |42 completes a circuit for maintaining slow to release relay |90 in energized positon before the same can deenergize, as follows: from ground by way of armature 333, conductor |23, armature |1|, armature |42, and through the winding of relay |90 to battery. At armature- |43 relay |40 completes the circuit for operating the connector test relay 390 as follows: from grounded lock conductor I4, armature |43, conductor |31, and throughy the lower winding of relay 300 to battery. At armature 305 relay 300 completes a locking circuit for itself from grounded lock conductor I4, at armatures 30| and 306 again prepares the ringing circuit, at armature 383 again connects relay 390 to the pick-up conductor, and at armature 384 grounds test conductor 3 by way of armatures |33, 293 and 2|3 for holding the cut-oit relay 1 energized and the line busy.

From the foregoing it will be seen that in response to the calling subscriber replacing his receiver after receiving a busy signal on making a reverting call that the cut-off relay in his own line circuit is maintained in operated position, that the reverting call relay |40 in the link is operated` while the slow to release relay |90 is maintained in operated position, and that the connector test relay 300 is operated to cause ringing current in accordance with the code selecting digitv dialledtov be transmitted out over his own line to operate the ringers of the substations thereon. When the pick-up conductor in the code ringing interrupter is grounded` relay 399 is energized as previously described to connect the selected code ring conductor tothe called line.

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The bells on the called line are then rung in accordance with the code selected.

. In response to either the calling subscriber or the called subscriber answering, the following circuit for energizing relay |19 is completed during the silent period when relay 399 is in deenergized position. This circuit may be traced as follows: from ground at armature 341, armature 396, conductor ||5, armatures 29| and 2| I, conductor included in cable 4, through the substation loop to conductor 2, and thence over cable 4 to armature 2|2, armature 292, conductor I I4, armature 39 I, armature 392 and resting contact,y conductor |98, through the upper righth'and winding of repeating coil RC and through the winding of relay |19 to battery. At armature |12 and working contact of relay |19 again completes the circuit for energizing ring cutoff relay 344 to prevent the reapplication of ringing current to the called line, and at armature |1| opens the circuit of slow to release relay |99. After an interval slow to release relay |99 deenergizes and at armature |92 disconnects ground from conductor |24 to open the circuit of relays 3I3 and 339 to cause their deenergization. At armature |93 relay |99 disconnects ground from the connector lock conductor |29 to open the locking circuit-s of the operated connector unit relay 299 and the operatedV connector group relay 2 I9. At armature |94 relay |99 disconnects ground from the lock conductor |4 to open the circuits of relays |99, 344, and 399, the operated nder group relay I9, the operated finder unit relay 99, and the operated code selecting upon deenergizing, prepares the permanent disconnect circuit and the circuit to relay 369. Busy relay 339, upon deenergizing, at armature 336 opens the circuit of relay I49 to cause the latter relay to deenergize. Connector unit relay 299 and connector group relay 2 I9 deenergize and disconnect the line and test conductors of the called line Yfrom the link, thereby opening the circuit to back-bridge relay |19 and cut-oli relay 1. Finder unit relay 99 and nder group relay |9 deenergize and disconnect the line and test conductors of the line from the link. The operated code selecting relay deenergizes and restores the code selecting relay to normal position. Relay |99, upon deenergizing,

'- opens the talking conductors and prepares the start circuit for line relay |69. Cut-off relay 344, upon deenergizing, again prepares the pickup circuit. Test relay 399, upon deenergizing, at armature 394 disconnects the ground which has been maintaining the called line busy during this interval. Relays |49 and |19 deenergize to restore the link to its normal condition ready for use in other calls.

When cut-cil relay 'I deenergizes, said relay at armatures 18 and 11, completes the circuit for energizing line relay 8 over the subscribers loop. Relay 8, upon energizing, at armature 86 grounds conductor 3 to maintain this line busy at the called end of the link, and at armature 88 completes the locking circuit for slow to rele-ase relay 6 by way of armature 61, so that relay 6 will maintain armature 66 operated to prevent the application of calling battery to test conductor 9. Talking battery to the subscribers on this line is furnished through the windings of line relay 8. After conversation and in response to both subscribers replacing their receivers the circuit through line relay 8 is opened with the result that relay 8 now deenergizes. At armature 88 relay 8 opens the circuit of relay 6 which deenergizes after an interval to restore the line circuit to its normal position and at armature 86 removes the busying ground.

Trunk calls The local subscribers have access to one group of switch-through trunks. The group of trunks extends to a distant exchange and terminates in the 49-line group in the place of the last three lines in that group. In order for the link to automatically test and hunt for an idle trunk in the group, such trunk lines are provided with two test conductors, and all but the last trunk in the group has these two test conductors strapped together as shown by jumpers 245 and 249 for trunks 43 and 44, respectively. In order for a local subscriber to seize an idle trunk in the group, such subscriber will dial the digits 4 and 3 to connect with the first trunk in the group. In case this trunk is busy, the second trunk, or trunk 44,'is tested and should this trunk be busy then the third and last trunk is tested. at which point the connection is' completed if the trunk is idle and if this trunk should also be busy then the busy tone is transmitted to the calling subscriber.

When a calling subscriber initiates a trunk call the rlrst idle link is connected to the calling line in the same manner as previously described, `and. in response to the calling subscriber dialling the digits 4 and 3, after receiving dial tone, the connector unit relay 219 and the connector group relay 249 are operated in the same manner as previously described to connect the line and test conductors of the link to the line and test conductors of trunk line 43.

The operation from this point on is slightlyy different from that previously described and when the connector unit relay 219 is operated the following test circuit is completed to test for the busy condition of trunk 43. In case trunk 43 is busy, then ground will be connected to the test conductor of the trunk line and will extend by way of armature 243, the second upper armature of relay 219,`test conductor ||1, armature 215 on the operated connector unit relay 219, armature 246v on the operated connector group relay 249, switchthrough conductor IIB, through the lower winding of marginal switch-through relay |39, armature |8|, conductor |25, resistance 325, armature 322, and through the winding of two-step marginal busy relay 339. Switch-through relay |39 does not energize in series with resistance 325 and the windings of relay 339, but the two-step busy relay 339 operates over the above traced circuit to operate only armature 334 to prepare the circuit for energizing the latter relay to its second step. Shortly after the impulsing period following the second digit relays 3|9 and 329 de-A energize and relay 329 at armature 322 completes the circuit from grounded conductor |24 for operating busy relay 339 in its second step. At armature 335 busy relay 339 completes the circuit for energizing trunk hunting relay 349 as follows: from` ground on the busy test conductor of the called trunk line, armature 243, and thence by way of jumper 245 to armature 244, through the upper armature of relay 219, conductor 3|9, ar mature 3 2, armature 335, and through the winding of relay 349 to battery. At armature 34| relay 349 disconnects the busy tone from the upper talking conductor, at armature 342 opens the locking circuit of two-step busy relay 339, as well as preparing a new test circuit for maintaining busy relay 339 in energized position in case the next or second trunk 44 is busy, and at armature 343 connects ground to the trunk hunting conductor 299 to complete the circuit for energizing connector unit relay 25s as follows: from ground connected to the eXtra test conductor SIS by means of the ground extending from the trunk test conductor over jumper 245 as previously traced, armatures 3| 2 and 335, armature 343, conductor 299, armature 298, armature 288 and resting contact, armature 278 and working contact, and through the winding of connector unit relay 280 to battery. The release time of the connector unit relays are less than the energizing time, and relay 200, upon energizing, closes first its locking circuit at armature 23? and then operates its armature 285 to open the locking circuit of connector unit relay 270 to cause the latter relay to deenergize. At its upper armatures connector unit relay 280 connects the line and test conductors of the second trunk 44 to the link, at armature 225 maintains the switch-through circuit, at armature 283 and resting contact opens the original energizing lcircuit of relay 280, and at its working contact prepares and closes the circuit for relay 290 which is slightly slow to operate. Relay 250, upon deenergizing, at its upper armatures disconnects the line and test conductors of the rst trunk line or trunk 43 from the link. After connector' unit relay 270 deenergizes v and before connector unit relay 290 has had suiiicient time to fully energize the following test circuit is completed to determine if the seco-nd trunk or trunk 44 is busy or idle. If idle, busy relay 330 immediately falls back to open the circuit grounding the trunk hunting conductor 299 to prevent the energization of connector unit relay 290. I case the second trunk is busy, then busy relay 330 is maintained in energized position over the following circuit; from ground on the test conductor of the second trunk line, through the test armatures on the operated connector group relay 249 and the operated connector unit relay 280 to conductor IH and thence by way of armature |33 and resting contact, conductor ||0, armature 342 and working Contact, the normally closed springs controlled by armature 322, and through the winding of two-step busy relay 330 to battery. The busy ground on the test conductor of the second trunk line also extends through the jumper 249 through the extra test armatures on relays 240 and 290, extra test conductor 3| 9 and thence by way of armatures 3 l 2 and 335 for maintaining relay 349 in operated position. This same ground extended by way of armature 343 and trunk hunting conductor 299, armature 298, and armature 2290 and working contact through the winding of connector unit relay 290 for energizing the latter relay. At armature 291 relay 290 rst completes its own locking circuit to grounded lock conductor |26, at armature 296 opens the locking circuit of connector unit relay 280 to cause the latter relay to deenergize, at armature 298 opens itsoriginal energizing circuit, at armature 295 maintains the switch-through circuit, and at armature 29| to 294, inclusive, connects the line and test conductors of the third or last vtrunk line 45 to the link. Connector unit relay 280, upon deenergizing, at its upper armatures disconnects the line and'test 4conductors of the second trunk line from the link. As previously described, the last trunk line in the trunk group does not have its two test conductors connected together with a jumper such as the preceding trunks with the result that no further trunk hunting takes place, regardless of whether the trunk is idle or busy. In case the last trunk line 1s busy, then busy relay 330 is maintained energized but in this case since no connection is completed for the eXtra test conductor 3|!! the circuit to relay 340 is opened with the result that this relay now deenergizes. At armature 34| relay 340 connects busy tone to the upper talking conductor to cause the transmission of busy tone to the calling line, as previously described, and at the normally closed springs controlled by armature 342 completes the previously traced locking circuit for busy relay 330. When the calling subscriber hears the busy tone such subscriber will replace his receiver and release the link circuit in the same manner as previously described.

As soon as anl idle trunk is connected to the link the circuit for busy relay 330 is no longer completed with the result that this relay now deenergizes if energized, whereupon a circuit is completed for energizing the switch-through relay |30 as follows: from ground by way of armature |92, conductor |24, armature 334 and resting contact, armature 32|, conductor |25,-armature |8|, through the lower windingof switch-through relay l3ll, conductor I6, to armature 246 and through the operated switch-through armatures on the connector unit relay, such as armatures 295, 285 or 2'i5, conductor through the operated test armature on the operated connector unit relay, through the test armature on the operated connector group relay, such as armature 243, and thence by way of the test conductor of the idle trunk to battery thereon. At armatures |3| and |35 switch-through relay |30 switches the talking conductors and opens the circuit to line relay |50. -At armature |32 opens the impulsing circuit and the circuit to relay |80, at armature |33 opens the original test circuit and closes the circuit for holding slow to release relay |90 energized from ground fed back from the trunk over the trunk test conductor, at armature |34 locks itself through its upper winding from ground fed back over the trunk, and at armature |35 grounds conductor 19 by way of armature |05 to maintain the calling line busy and the cut-off relay 'I energized after the slow to release relay |80 deenergizes.

When relay |30 at armatures -|3| and |36 switches the talking conductors straight through to the called trunk, a circuit is completed in the trunk circuit for causing ground to be connected to the test conductor of the trunk line as follows: this circuit may be traced as follows: through the calling subscribers loop, conductors and 2, armatures and |2, 9| and 92, conductors I9 and 89, armatures |9| and |09, normally closed springs controlled by armatures |2| and |22, armatures |3| and |39 and their working contacts, conductors I4 and I5, through the operatedl line armatures on the operated connector unit and connector group relays over the negative and positive line conductors of the trunk line to ground and battery through the winding of a relay in the trunk line. The operation of this relay in the trunk line circuit causes ground to be connected to the test conductor of the trunk for maintaining slow to release relay |90 in operated position. This circuit may be traced from ground on the trunk test conductor through the operated test armatures of the operated connector unit and connector group relays, test conductor armature |33 and working Contact, and through the Winding of relay |99 to battery. Marginal switchthrough relay |30 is maintained energized over its upper winding from grounded test conductor |1, by wayof armatures, such as armatures 295, 285,01' 215, on the' operated connector' unit relay, armature 246,'switch-through conductor IIB, armature |34 and throughthe upper winding of switch-through relay |30 to battery.

Line relay |60 and later on relay |80 deenergize. At armature |8| relay |80 opens the original energizing circuit of switch-through relay |30 and at armature |82 opens the original energizing circuit of slow to release relay |90 which is now held energized from ground senty back over the-test conductor of the trunk line. The subscribers line is now connected direct to the line conductors of the trunk line and the subscriber now dials the number of the desired main exchange subscribers line in case the trunk terminates in an automatic exchange, or the operator completes the connection to the main exchange subscriber in the well-known manner in case the trunk terminates in a manual exchange. Talking battery to the local subscriber is furnished from the main exchange over the trunk line.

The release ofv the local link circuit is controlled from the main exchange, andin response to the main exchange subscriber replacing his receiver or the operator disconnecting, ground is is removed from the test conductor of the called trunk line to cause the'deenergization of relays |30 and |90. Relay |30, upon deenergizing when ground is removed from the test conductor of the trunk line, at armature |35 disconnects ground from conductor 19 to open the circuit of cut-off relay 1 to cause the latter relay to deenergize. Slow to release relay |90, after an interval deenergizes and causes the deenergization of the operated iinder unit and finder group relays, the deenergization of the operated connector unit and connector group relays and the deenergization of relay 313, thereby restoring the link circuit to its normal condition for use in other calls.

When an incoming trunk call is made on one of the trunk lines the line relay in the trunk line grounds the start conductor, similar to start conductor or 5 for this line group, to cause the operation of the finder unit and group relays as previously described, to connect the callingl end of the link to the trunk line. The main exchange subscriber after hearing the dial tone then dials the local subscribers number and the connection is completed in the same manner as previously described.

Permanent lines Permanent lines are lines which are shorted or grounded due to some fault and in some cases of trouble they cause the line relays, such as line relay 8, to operate and initiate a call the same as when a subscriber initiates acall. In case of trouble of this nature the finder unit relay and the nder group relay operate as before to connect the line to an idle link.V This link is held by the permanent line. When all the links become busy ground is disconnected from the all link busy conductor ALB in Fig. 3 by the operation of all the relays |90 in all of the links. A predetermined time after ground is disconnected from the all link busy conductor ALB the permanent disconnect lead Perm. Disc; is grounded. Since no dialling has taken place relay 3|3 is not energized and when the permanent disconnectv lead is grounded relay |40 is energized in the following circuit: from grounded permanent disconnect lead Perm. Disc. armature 3|6, conductor |21, and relay |40 to battery. At arma- 751; tures |4| and |44 relay |40l opens the talking conductors extending to the line with the result that line relay i60 now deenergizes. Shortly thereafter relay |80 deenergizes to open the circuit of relay |90 at armature |82, and at armature |83 opens the circuit of the cut-oit relay in the line circuit. After an interval slow to release relay |90 deenergizes to accomplish the same functions as previously described, and at armature |94 and its resting Contact grounds the all link busy conductor ALB to cause ground to be disconnected from the permanent disconnect conductor Perm. Disc. When ground is disconnected from the permanent disconnect conductor relay |40 d eenergizes and this link circuit is now available for use with other lines. When the cut-01T relay, such as relay 1, deenergizes in response to the operation of relay |40, cut-off relay 1 reconnects the line relay, such as 8, across the line con.- ductors to cause the line relay to again energize. Since relay 6 is a slow to release relay the energization of relay 8 at armature E8 completes the locking circuit for relay 6 by way of armature 61 before the relay 6 can de-energize. At armature 86 line relay 8 maintains this line busy to prevent connection thereto, while the operation of relay 0 maintains the start circuit 5 open. Relays 8 and 6 are maintained until the trouble is cleared.

The invention having been described, What is considered to be new is pointed out in the appended claims.

. What is claimed is:

l. In a telephone system, groups of lines, a plurality of links for interconnecting said lines, a rst and a second relay group in each of said links, means responsive to a line in one of said groups initiating a call for marking such lgroup as calling and for seizing an idle one of said links, means responsive thereto for operating therelay corresponding to the calling group in the iirst relay link group, means operated by said relay for marking the calling line in the second relay link group, and means yfor thereafter sequentially operating the relays inthe second link group to test for and nd the marked calling line.

2. I n a telephone system, a group of lines, each line having a test conductor, a link for interconnecting said lines, a relay in said link corresponding Ato'said group of lines, a group of relays in said link, means responsive to a line in said group initiating a call for marking its individual test conductor with calling potential and for operating said link relay to connect all the test conductors of said group of lines to said group of relays, means for thereafter sequentially operating the relays in said group in search of the test conductor having calling potential thereon, and means operated when the calling potential is found for stopping further sequential operationv of said relays.

3..'.ln a telephone system, groups of lines, a group of relays common toV said lines, means responsive to the initiation of a call on a line in one of said groups for marking that group ywith calling potential in the relay group, means operated responsive thereto for sequentially operating said relays in search of said calling potential, and means operated when said calling potential -is found for stopping further sequential operation of said relays. u

4. rIn a telephone system, a group of lines comprising both a link-for interconnecting said lines, a group of relays in said link, each of said relays correspond-l subscribers lines and trunk lines;

"zol

for operating the relay in ing to a line in said group, testing meansinv said link, and means responsive to a calling subscriber dialling the number designating a trunk call in this group of lines for sequentially operating the relays corresponding to the trunk lines in this group of lines to successively connect the trunk lines to said testing means until an idle trunk line in the group is found.

5. In a telephone system, a group of lines comprising both subscribers lines and trunk lines, a link for interconnecting said lines, a group of relays in said link, each of said relays corresponding to a line in said group, testing means in said link, a circuit controlled by each of said relays When operated for connecting the line corresponding to such operated relay to said testing means, means for operating said relays to conneet the subscribers lines in said group over said circuits to said testing means in response to a calling subscriber dialling the numbers designating the calls to subscribers lines in said group, and means for sequentially operating the relays corresponding to said trunk lines to successively connect the trunk lines of said group to said testing means until an idle trunk line is found in case the calling subscriber dials the number designating a trunk call in this group.

6. In a telephone system, groups of lines, one of said groups comprising bothl subscribers lines and trunk lines and some of said groups comprising only subscribers lines, a link for interconnecting said lines, a group of relays in said link, each said relay corresponding to a line in each of said groups of lines, testing means in said link,

l means responsive to a calling subscriber dialling the group digit of a called subscribers number for connecting the group of lines corresponding to said digit to said relay group, means responsive to the calling subscriber dialling the units digit said group corresponding to the called line in this group, circuits completed by the operation of each relayy of said group for connecting only the line of the connected group corresponding to such operated relay to said testing means, and means responsive to a calling subscriber dialling the number designating a trunk call in said one group of lines for connecting such group of lines to said relay group and for sequentially operating the relays in said group corresponding to successive trunk lines in this group to successively connect such trunk lines to said testing means until an idle one of said trunk lines in the group is found.

7. In a telephone system, a calling line, a called party line, means responsive to a subscriber on the calling line initiating a call and dialling a plurality of digits of a called subscribers number on said called line for extending a connection to the called line, code selecting relays operated responsive to the calling subscriber dialling the last digit of the called subscribers number for signalling the called subscriber onthe called line in case the called line is idle, a testing circuit over which the called line is testedfor its busy or idle condition, and contacts operated on the rst code selecting relay in response to the first impulse of the last digit for completing said testing circuit.

8. In an impulse repeating arrangement, a line relay and a line over which it is energized, a pulse relay, a third relay controlled by said pulse relay, a circuit for said'pulse relayjointly controlled by said line relay and said third relay,` and means including said pulse relay for energizing said I third relay. in response to each alternate energi`A zation of said line relay and for deenergizing said third. relay in response to the other alternate energizations, of said line relay when a series of impulses is transmitted to. said line relay over said line.

9. In a telephone system, subscribers lines and trunk lines, an all relay finder-connector link, relays in said. link, means responsive to calls for operating said relays to' complete localconnections between subscribers lines andtrunk connections between trunk lines and subscribers lines, a source oftalking battery in said link, a source of talking battery in each` trunk line, means for feeding talking battery from'saidy link to the calling; and called subscribers linesinlocal.connections, and means for disconnecting said link source and for feeding talking battery from; the trunk line source to a subscriber connected in.a trunk connection.

10. In a telephone system, groups of. lines, a plurality of, links for interconnecting said lines, a groupI of relays ineachllink, each relay in each groupcorresponding to a group of lines and correspending relays in diierent relay groups correspending to the same groupV ofA lines, contacts oncalling line is in to mark. the calling group'in each link, agroup'test relay in each link, means alsoy responsive tothe initiation of said call for seizing an idle one of saidlinksand for sequentially operating the group relaysin the seized link tond said calling potential? andconnect such calling potential throughthe operated contacts of the corresponding group relay to the group test relay in said. responsive theretofor energizing said group test relay to prevent further sequential operation ofA said group relays.

12. In a telephone system, groups of lines, a plurality of links for interconnecting said lines, a rst and a second-group-of-'relays in each link, each relay4 in veach rst group correspondingto a group of lines andcorresponding relays in different iirst groups-corresponding to the same group of lines, each relay in each second-group corresponding toaline in each-of said group of lines and corresponding; relays in different second groups corresponding` to the same line,- means. responsive to` the initiationpf 13. In a telephone system, groups of: lines,. al pluralityof links common lto said lines, a first and alsecond group .of relays in `each link, there being a firstgroup relay Ain :each link for each group of lines and veach such relayahaving contacts for connectingfall thev lines-of .its corresponding-group to theassociatedsecond group relays inrthesame to thecontacts of` thev relay in each linkcorresponding to the group the.

link, anda circuit completed.

a, callron one. ofV said lines for seizing lan idle one ofsaid links, for; then sequentially 'operating the relays in the liirstl in .thesecond `group of V nd thefcalling line in said first group relays link. there being 'as many second group reiays in each link as there are lines in any one group and each such relay having contacts for connecting a given line in any group dependent upon which one of the associated first group relays is operated, means responsive to the initiation of a call on one of said lines for connecting group calling potential to the group relays in each link and for marking the calling line With line calling potential, means also responsive to the initiation of a call for seizing an idle one of said links, means responsive to said seizure for sequentially operating the first group relays in the seized link to nd the group calling potential, means responsive to finding said group calling potential for stopping further sequential operation of said first group relays and for connecting said line calling potential to the second group relays in said link, and means responsive thereto for sequentially operating the second group relays in the seized link until said line calling potential is found toy operatively connect the calling line to said link.

14. In an impulsing system, an impulsing relay, an impulse repeating relay, means for deenergizing said impulsing relay a plurality of times to transmit impulses, means for energizing said repeating relay in response to each odd impulse transmitted by said impulsing relay and for deenergizing said repeating relay in response to each even impulse transmitted by said impulsing relay, selecting means, an odd and an even pulse conductor extending to said selecting means, and contacts on said repeating relay for grounding the odd pulse conductor on each energization of said repeating relay and for grounding the even pulse conductor on each deenergization of said repeating relay to operate `said selecting means to make a selection.

15. In an impulsing system, an impulse repeating relay, an odd and an even pulse conductor, means for energizing and deenergizing said impulse repeating relay a plurality of times, a group of selecting relays, means for energizing the first selecting relay in response to the first energization of said impulse repeating relay, means for energizing the second selecting relay over said even pulse conductor in response to the first deenergization of said impulse repeating relay, means for energizing the third selecting relay over said odd pulse conductor in response to the second energization of said impulse repeating relay, means for energizing the remaining selecting relays over said even and odd pulse conductors in the manner set forth in response to subsequent deenergizations and energizations of said impulse repeating relay, and a locking circuit for each selecting relay except the last controlled by the succeeding selecting relay.

16. In an impulsing system, an impulse repeating relay, an odd and an even pulse conductor, means for energizing and deenergizing said impulse repeating relay a plurality of times, a group of selecting relays, means for energizing the first selecting relay in response to the first energization of said impulse repeating relay, means for energizing the second selecting relay over said even pulse conductor in response to the rst deenergization of said impulse repeating relays, means for energizing the third selecting relay over said odd pulse conductor in response to the second energization of said impulse repeating relay, means for energizing the remaining selecting relays over said even and odd pulse conductors in the manner set forth in response to subsequent deenergizations and energizations of said impulse repeating relay, a locking circuit for each selecting relay for maintaining the same energized, means controlled by veach succeeding selecting relay upon energizing for opening the locking circuit of the preceeding selecting relay to cause its deenergization, and means for preventing the reenergization of any preceding selecting relays in response to the energizations and deenergizations of said impulse repeating` relay. f

17.'In a selecting system, an impulse repeating relay, an odd pulse conductor andan even pulse conductor, means for energizing and deenergizing said repeating relay a plurality of times, a lock conductor, a group of selecting relays, means for connecting said lock conductor to the vrst selecting relay for energizingthe same in response to the first energization of said repeating relay, means controlled by said first selecting relay for completing a locking circuit for itself including said lock conductor and for connecting the second selecting relay to said even pulse conductor, said second selecting relay energized over said even pulse conductor in response to the nrst deenergization of said repeating relay, means controlled by said second selecting relay for completing a locking circuit for itself including said lock conductor, for opening the locking circuit of the first selecting relay to cause its deenergization, and for connecting the third selecting relay to said odd pulse conductor, said third selecting relay energized over said odd pulse conductor in response to the second energization of said repeating relay, means controlled by said third selecting relay for completing a locking circuit for itself including said lock conductor, for opening the locking circuit of the second selecting relay to cause its deenergization, and for connecting the fourth selecting relay to said even conductor, and the remaining selecting relays energizing over connections to the even and odd pulse conductors prepared by the preceding relay, locking over the lock conductor, and deenergizing when the succeeding relay is energized in the manner set forth in response to subsequent deenergizations and energizations of said repeating relay to make a selection.

18. In a telephone system, a link circuit, a group of trunk lines accessible to said link circuit, a first and a second test conductor for each trunk line, connecting means permanently connecting the first test conductor With the second test conductor on each trunk line except the last in said group, means for energizing the relay corresponding to the first trunk line in the group to connect such trunk line to said link circuit, a circuit including the first and second test conductors and the associated connecting means of the rst trunk line for energizing the relay corresponding to the second trunk line in case the rst trunk line is busy to connect the second trunk line to said link circuit, and means controlled by the energization of the second trunk relay for deenergizing said first trunk relay to disconnect the first trunk line from said link circuit.

19. In a telephone system, a group of lines comprising both subscribers lines and trunk lines, a link for interconnecting said lines, a group of relays in said link circuit, each of said relays corresponding to a line in said group, testing means in said link, means responsive to a calling subscriber dialling the group digit of a called subscribers line in said group for connecting said group of lines to said relaygroup, means responsive to said subscriber dialling the unit digit for operating the relay corresponding to the called line, circuits completed by the operation of each said relay for connecting only the line corresponding to such operated relay to said testing means, and means responsive to the calling subscriber dialling the number designating a trunk callin this group of lines for operating said rst means to connect this group of lines to said relay group for operating said second means to connect the rst trunk in the group, and for thereafter sequentially operating the remaining relays in said group corresponding to the successive trunk lines to successively connect such trunk lines to said testing means until an idle one of said trunk lines is found.

20. In a telephone system, a group of lines comprising subscribers lines and trunk lines, each line having -a test conductor, a link for interconnecting said lines, a relay in said link corresponding to said group of lines, a group of relays in said link, each of said group relays corresponding to a line in said group, means responsive to a calling subscriber dialling the number designating a trunk call in this group of lines for operating said relay to connect the test conductors of all said lines to said group of relays, testing means in said link, and means also responsive to the calling subscriber dialling the number designating a trunk call for sequentially operating the relays in said relay group corresponding to the trunk lines in this group of lines to successively connect the test conductors of successive trunk lines to said testing means until an idle trunk line in the group is found.

HARRY G. EVERS. 

